DE2758492A1 - COMBUSTION PROCESS IN A TWO-STROKE COMBUSTION ENGINE AND COMBUSTION ENGINE OPERATING AFTER THE PROCESS - Google Patents

Description

Combustion process in a two-stroke internal combustion engine as well as internal combustion

engine

It is known that in two-stroke internal combustion engines without With the aid of spark plugs a spontaneous ignition of the fresh Fuel gas mixture can be generated. The burn that caused by the self-ignition mentioned is usually referred to as extraordinary combustion or run-on. If the engine is running at high speed under low load, with the mentioned self-ignition occurring, the proportion is of exhaust gas residues in the cylinder of the machine is much larger than that of fresh fuel gas mixture. The fresh fuel gas mixture is therefore heated up and transformed by the heat of the exhaust gas residues present in the cylinder, as a result of which free radicals are generated in the fresh fuel gas mixture. An atmosphere in which such radicals are present is referred to below as an active thermal atmosphere. If an extraordinary Combustion of the type mentioned above takes place, but then the active thermal atmosphere at the beginning of the compression stroke eliminates hot spot ignitions, misfires and finally the detonation caused by the spark plug in a running sequence, which in turn results in major changes in the torque output on the machine. Since the Exceptional combustion brings the disadvantages outlined above with it, it is generally undesirable.

The inventor has investigated the problem described and has found that when the active thermal atmosphere, at the beginning of the compression stroke by the extraordinary combustion is generated until the end of the compression stroke is maintained, a self-ignition of the active thermal atmosphere in the

Combustion chamber is caused without being removed from the spark plug

will ignited and that a combustion of the active thermal

atmosphere takes place. It was also found that this Type of burn; the machine runs very smoothly j leads even if you have a lean fuel-air mixture used. One can reduce fuel consumption in this way and reduce the proportion of pollutants in the exhaust gases.

The invention is based on the object of a combustion process to be specified in a two-stroke internal combustion engine, which is suitable for long-term operation of the machine even under partial load.

This object is achieved by the invention specified in claim 1. Developments of the invention as well as a Internal combustion engines operating according to the method are the subject matter the subclaims.

The invention is described below with reference to the drawings are explained in more detail using various exemplary embodiments of internal combustion engines. It shows:

Fig. 1 is a side view of a two-stroke internal combustion engine according to the invention in longitudinal section;

FIG. 2 is a front view of the machine according to FIG. 1 in longitudinal section t;

3 is a plan view of a crankcase;

Fig. K is a front view of the crankcase part 1a;

Fig. 5 is a front view of the crankcase part Ib;

6 shows a section along the line VI-VI in FIG. K;

7 shows a perspective illustration of a section the crankcase;

8 shows a section along the line VIII-VIlI in FIG. 7;

9 is a side view of another two-stroke engine machine in longitudinal section j

Figure 10 is a longitudinal front view of the machine of Figure 9 cut ;

Fig. 1 1 is a plan view of the crankcase in the Mcischine according to Fig. 9;

FIG. 12 is a front view of the crankcase 1a of FIG Fig. 9;

13 shows a partial longitudinal section through a further embodiment the invention;

Fig. 1 ¹ I a graphical representation of the relationship between the throttle valve opening and the exhaust control valve, and

15 shows a partial longitudinal section through a fourth embodiment the invention.

First of all, FIGS. 1 and 2 are considered. A cylinder block 2 is fastened to a crankcase 1, on which cylinder head 3 is in turn fastened. A cylinder bore 5 is made in the cylinder block 2, in which a piston h with an approximately flat piston head is guided so as to be movable up and down. The piston crown, together with the cylinder block 2 and the cylinder head 3, delimits a combustion chamber 6. In the

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Cylinder head 3 is a spark plug '/ screwed into the crankcase A crank chamber 8 is formed, in which a counterweight 9 is located, to which a connecting rod 10 is hinged. A suction line opens into the crankcase, 11 with an intake channel 12 formed therein. Λη the intake line 11 is flanged a carburetor 13, in which a throttle valve 1Ί is located. With 15 there are two overflownüffniin (; en designated. There is an outlet pipe socket on the Zy 1 country block formed, the cylinder-side opening with 16 and to which an outlet line 17 is flanged is, which encloses an outlet channel 18 “In the intake channel 12 a itückschl agventi I 19 is arranged, which the inflow of fresh fuel gas mixture in the crankcase 8 permitted.

The two-stroke engine shown in Figures 1 and 2 from Schnürle type has an effective compression ratio of 6.5: 1. As can be seen from Fig. 2, there is the crankcase 1 from three parts 1a, Ib and Ic. Two overflow channel 2O, the open at the openings 15 in the combustion chamber 6 are formed in the cylinder block 1 and are available with corresponding About trömkaiiiil en.? 1 in connection, which is in the upper part of the Crank housing 1 are formed. The one described, from the Partial channels 20 and 2 1 existing overflow channel is below referred to as the second transfer channel.

Fig. '(Shows the inner wall of the crankcase part 1a, Fig. 5 shows the inner wall of the crankcase part 1c. As can be seen from both figures, a pair of grooves 22a and 22b are formed in the inner walls of these crankcase parts, which run circular in the hand area to the center of the crankcase in the inner wall parallel to the grooves 22a and 22b a wider, flat groove 23 of width L, which is provided in the middle with a deeper groove 2k (see also FIG. 6). The dashed line K shows the outer boundary of the crankcase 8. When the crankcase parts la, 1b

and Ic are assembled, then the grooves 22a, 22b, 23 and 2'Ί lie between the crankcase part 1b and the crankcase part 1a or 1c (Fig. 6). As can be seen from Figures k and 5, the grooves 22a and 22b united with one another at their lower ends 25. One end 26 of the groove ZU is connected at 25 via a radially extending short groove 27 with the grooves 22a and 22b. The other end 2h is connected to the crank rail 8 via a short, radially extending groove 29. An annular disk 30 is fitted in the shallow groove so as to cover the groove 2h (Fig. 6).

Fig. 6 shows a cross section along the line VI-VI in Fig. H in the assembled state of the crankcase parts la and 1b. As shown in Fig. ¹ I and 6, each of the grooves 22a, 22b, 2U, 27 and 29, a channel is formed. As FIG. 7 shows, a groove 31 is formed in the inner wall of the crankcase part 1b at the bottom of the crank chamber 8, into which the mouth of the short radial groove 29 opens. As FIG. 8 shows, the bottom of the groove 31 is designed so that this groove becomes deeper from the center towards both ends.

With broken lines in Figures 1 to 5 channels 33a, 33b and 3 ^ a, 3 ^ b are drawn, which open into the overflow channels 21 and these with the upper ends 35 ^a t 35b (Fig. H and 5) of the grooves Connect 22a and 22b in such a way that there is a relatively smooth transition between these connecting channels 33a, 33b and 3ha. _t 3 ^ b and the grooves 22a and 22b results. The connecting _{channel pairs 33a f} 33b and 3 ^ & »3 '· *> are arranged so that the axes of the channels 33» and Jka. intersect with the axes of the channels 33b and 3'Jb at an angle. The channels therefore open out, as shown in FIG. 3, at opposite corners into the lower end of each overflow channel, so that a fresh mixture from the crankcase forms in this when overflowing

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violent touch of the various communication channels gases flowing towards one another results, which has a reduction in the flow velocity of the gases as a result.

As is apparent from the preceding description, each overflow channel 21 is connected to the crank chamber 8 via the connecting channels and the grooves described. The channel, which consists of the connecting channels 33a, 33b and 3 ^ a, 3Uh _t the grooves 22a and 22b, the radial short groove 27 »of the groove 2k and the radial short groove 29, is referred to below as the first overflow channel. The crank chamber 8 is therefore connected to the combustion chamber 6 via the aforementioned first and second transfer channels.

In operation, the fresh fuel gas mixture sucked into the crank chamber 8 via the suction line 12 and the check valve 19 is gradually compressed during the downward movement of the piston k and pressed through the short radial groove 29 into the first overflow channel. It then flows through the first connecting channels at high speed, since the first overflow channel has a very small cross section. The fresh gas mixture then flows into the second transfer channels. Since the fresh gas mixture must flow at high speed in the first overflow channels, the flow energy is added to the fresh gas mixture and, as a result, the evaporation of liquid fuel components is improved during this time. The vaporized fresh gas mixture then flows into the second transfer channels. Since the gas flows flowing into the overflow channels from the various connecting channels come into very lively contact with one another, they lose kinetic energy. Since the overflow channels 21 have a much larger cross section than the connecting channels 33a, 33b and 3 ^ a, 3 ** b, the speed of the gas flowing into the overflow channels 21 is very suddenly reduced. That

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Fresh gas mixture moves upward in overflow channels 21 and 20 at slow speed. These are equipped with smooth inner walls. It then flows into the combustion chamber C at low speed as soon as the piston h has released the transfer openings 15. Even if the pressure in the crank chamber 8 at the point in time at which the piston h opens the overflow openings 15 is much greater than in the combustion chamber 6, the fresh gas mixture cannot flow into the combustion chamber 6 at high speed because the first overflow channels are small due to their small size Cross-sections act as chokes. The flow rate of the fresh gas mixture is therefore low during the entire flow process into the combustion chamber. The flow rate of the exhaust gases flushed out of the combustion chamber 6 by the fresh gases is therefore extx'era low and, as a result, it is avoided that the heat in the Iiestgasen is quickly lost. In addition, at the beginning of the compression stroke when the engine is under partial load, there is a large proportion of exhaust gas residues in the combustion chamber 6. Since this portion has a high temperature, the combustible fresh gas mixture is heated until radicals are formed, as a result of which an active thermal atmosphere is generated in the combustion chamber 6.

Since the gas flows in the combustion chamber 6 are extremely slow during the compression stroke, occur in the combustion chamber 6 hardly any turbulence and the heat transfer from the gases to the inner walls of the cylinder is as low as possible. The temperature of the gas in the combustion chamber 6 is increased further during the compression stroke. As a result, the proportion of radicals generated also increases. When radicals are generated, what is known as pre-combustion begins. If, towards the end of the compression cycle, the temperature of the gas in the combustion chamber 6 becomes very high

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a hot flame that causes self-ignition which does not come from the spark plug 7. Slow combustion ^{1 then} takes place, which is influenced by the exhaust gas guides. When the piston moves downward and the mouth 16 of the outlet channel 10 opens, the exhaust gases escape from the combustion chamber into the exhaust gas channel 18.

To bring about the combustion of the active thermal atmosphere, it is first necessary to create a high flow velocity in the first overflow channels in order to completely evaporate liquid fuel components. Then it is still necessary to cause a large delay in the gas flow so that the fresh gas flows into the combustion chamber 6 at a low speed. To achieve the high flow speed in the first overflow channels, these are very long and have small cross-sections. In order to achieve a high flow velocity in these first overflow ducts, it is advantageous if they are as smooth as possible. On the other hand, it has also been found that a high flow rate can also be achieved when there are relatively sharp bends in the flow path, for example at the transition from the groove 2h to the grooves 22a and 22b or at the transition from the groove 29 to the groove 2k ,

When the fresh fuel gas mixture flows into the combustion chamber 6 from the overflow openings 15, the radicals generated in the vapor phase within the contact area between the fresh gas mixture and residual exhaust gas. Where the fresh gases in Come into contact with the inner wall of the combustion chamber 6, no radicals are generated. It is therefore favorable to use the Schnürle machine as a two-stroke machine, which has two overflow openings 15 which are arranged so that the gases flowing into the combustion chamber 6 from them

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come in contact with each other and each other from the Deflect walls of the combustion chamber 6 and into the combustion chamber are surrounded by the ab ;; asrest. It can however, a two-stroke engine of other types of durations can also be used if it is so designed that the fresh gases are surrounded by the exhaust gas residues.

The fresh in the Kurbclraum 8 through the inlet channel 12 during the upward movement of the piston Λ · air-fuel drawn in by this The mixture consists of a high proportion of liquid Fuel on. This liquid fuel is deposited on the dodcn of the crankcase 8. However, if the open end of the first overflow ducts located in the bottom area of the crankcase 8, as is the case here, then the liquid fuel is in the first transfer channels together with the air-fuel mixture pressed in and evaporated there due to the conditions explained above. It is therefore possible to use the combustion chamber 6 the fuel in a proportion corresponding to the respective load, i.e. depending on the opening state of the Throttle valve 1 * i, to be supplied.

The usual two-stroke machines are used to reduce the The flow resistance to which the fresh fuel gas mixture is exposed when the machine is subjected to high loads is common, the length of the Make the overflow channel so short that it is in the upper area of the crankcase opens into this. A conventional one Machine of this type, however, has the disadvantage that a large proportion of the fresh gas contained / liquid fuel precipitates at the bottom of the crankcase when the engine is started, that introduced into the combustion chamber This makes mixture extremely lean, which is why it takes a long time to ignite this mixture. A conventional one Machine also has the disadvantage that due to the high negative pressure generated in the crankcase after the ignition

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lJoden nii '(lori';nschla;; eno liquid fuel immediately evaporates v; ii'd and as a consequence of this an extremely fine mixture is supplied to the combustion chamber, which leads to misfiring 'these disadvantages are findunc avoided since the first transfer ports at the bottom of the crank raunis start ,, addition, since the groove 31 is formed in the testes of the crank room portion 1b, is in the groove' J \ niedergcschla ;; ono of fuel through the thy Counterweight 9 caused l-uf lst.riimim, 'ien wec ^ cbblasen, As a result of this, the pre-evaporation of the liquid fuel contained in the crankcase is promoted. then the flow of the liquid fuel into the grooves is still promoted.

Figures 9 to 12 show a second embodiment the invention. Those parts that are identical to those of the first embodiment corresponded, have been given the same reference numerals, so that a more detailed explanation is dispensed with can. The overflow channel 21 is formed here in the crankcase part 1b and the upper ends 35a and 35b of the grooves 22a and 22b are formed on the crankcase parts 1a and 1c and are connected via the connecting lines 33a, 33 ^> and 3 ^ a, 3 ^ b » which are formed in the crankcase part 1b, connected to the lower end of the overflow channels 21. Again intersect the axes of these connecting lines within the overflow channels 21 at an angle so that the flowing in there Gases collide violently.

Vie wüluit before, it is to maintain an active Thermal atmosphere until the end of the compression stroke necessary that the turbulence and the flow velocities of the Exhaust gas residues in the combustion chamber 6 are as small as possible. Two causes of turbulence and currents of this Exhaust gas residues are an abrupt blowout of exhaust gases through the

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Outlet opening 16 and disturbances due to the pulsating pressure of the exhaust gas In order to avoid the abrupt blow-out and these disturbances, it is advantageous, as shown in FIG. 1 k shows the relationship between the degree of opening of this valve and that of the throttle valve 14. The relative opening of the exhaust gas control valve 36 is plotted on the ordinate X and the relative opening of the throttle valve 1 * f is plotted on the abscissa Y. As is apparent from Fig i'l., The exhaust control valve 36 is first gradually opened and then fully opened before the throttle valve IU reaches a position which corresponds to ⁰ Yes 30 of the full opening cross-section. The exhaust gas control valve 36 is then fully opened, will continue to open throughout the throttle \ h.

When the machine is only operated under low load 15 shows, it is advantageous to arrange a throttle element 37 with a fixed cross-sectional area in the exhaust gas duct 18. Additionally it is to prevent one abrupt blowing out of the exhaust gases through the outlet opening 16 favorable when the volume between the opening 16 and the exhaust gas control valve 36 is smaller than the volume of the combustion chamber 6 in UT-graduation of the piston. At one machine after According to the present invention, the spark plug 7 is used during the warm-up of the engine and when it is under severe conditions Load is running. It is not necessary to use the spark plug 7 when the engine is operated at part load because the combustion of the active thermal atmosphere takes place here,

According to the present invention, a two-stroke machine that can be operated very smoothly under partial load, * The combustion of an active thermal atmosphere brings about a considerable reduction in the proportion of pollutants in the Exhaust fumes and reduces fuel consumption.

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Claims (31)

Expectations Combustion process in a two-stroke internal combustion engine with a crank chamber, a combustion chamber and a transfer passage connecting the crank chamber with the combustion chamber, performing the following steps Introducing a fresh fuel gas mixture into the crankcase; Introducing the fresh fuel gas mixture into the overflow channel; Introducing the fresh fuel gas mixture into the combustion chamber, characterized by the following substeps and further steps a) causing a high flow velocity in the overflow channel for the evaporation of liquid fuel components; b) decelerating the flow velocity in the overflow channel; c) Maintaining a low flow rate when Introducing the fresh gas mixture into the combustion chamber and suppressing currents and turbulence in the exhaust gas present there; ORIGINAL INSPECTED 809828/0689 MUNICH: TELEPHONE (O8O) 39 SS SB CABLE: PROPINOUS TELEX OO 94 944 BERLIN: TELEPHONE (O3O) 8 3) 30 88 CABLE: PROPINDUS ■ TELEX O184OS7 d) Creating an active topic atmosphere in the Combustion chamber at the beginning of the compression stroke; e) Maintaining the active thermal atmosphere until End of the compression stroke and reforming of the fresh gas mixture, and f) causing the fresh gas mixture to self-ignite . 2. The method according to claim 1, characterized in that the Gas mixture flowing in the overflow channel is braked abruptly. 3. The method according to claim 2, characterized in that the The direction of flow in the overflow channel is suddenly changed, h _a method according to claim 3 »characterized in that two fresh gas flows collide in the overflow duct. 5. The method according to claim 2, characterized in that the fresh gas mixture flows into a room of large volume. 6. The method according to claim 1, characterized in that the fresh gas mixture in the overflow channel with a long way high speed and a short way with low Speed flows. 7. The method according to claim 6, characterized in that the fresh gas mixture flows smoothly on the long way. 8. The method according to claim 7, characterized in that the fresh gas mixture on the entire path of the overflow channel flows smoothly at high speed until it decelerates. 9. The method according to claim G, characterized in that the fresh gas mixture at low speed after the Braking in the overflow channel flows smoothly. 10. The method according to claim 1, characterized in that the fresh gas mixture in the crankcase at the bottom of the same in the Transfer channel is pressed. 11. The method according to claim 10, characterized in that the liquid precipitated at the bottom of the crankcase Fuel is passed into the transfer channel. 12. The method according to claim 1, characterized in that the abrupt outflow of exhaust gas from the combustion chamber is prevented to low currents and turbulence in the exhaust gas of the combustion chamber and the exhaust gas at a high temperature to keep. 13 · The method according to claim 12, characterized in that it is only carried out when the machine is under partial load. 14. The method according to claim 1, characterized in that the fresh gas mixture in the center of the combustion chamber is directed. 15. Two-stroke internal combustion engine with a cylinder with a Cylinder bore and outlet opening, a reciprocating piston which delimits a combustion chamber in the cylinder bore, a crankcase with into the crankcase opening intake duct which connects the crankcase and the combustion chamber to one another, characterized in that, that the overflow channel into a first overflow channel (29, 2 '*, 27, 22a, 22b, 33a, 33b, 3i »a, 34b) of small cross-section and a second, overflow channel (20, 21) with a large cross section is divided, which latter opens into the combustion chamber (6). 809878/068 $ 16. Internal combustion engine according to claim 15 ι characterized in that the first overflow channel relative to the second
Overflow channel is long. 17. Internal combustion engine according to claim 16, characterized in that the first overflow duct has two branch ducts (22a,
22b) which includes the second overflow channel (20,21)
connect your crankcase (8). 18. Brennkraf Lniaschxne according to claim 17, characterized in that the Ziveigkanäle (22a, 22b) via a common channel (2h) are connected to the crank chamber (8). 19 internal combustion engine according to claim 18, characterized in that that the branch channels (22a, 22b) have equal lengths and no sharp kinks. 20. Internal combustion engine according to claim 17 _t characterized in that the Zveigkanäle (22a, 22b) of connecting channels
(} hi \, jhh) which in turn end in the bottom of the second
Overflow channel (-20,21) open _c 21. Internal combustion engine according to claim 20, characterized in that that the connecting channels (3 '* a »3 ^ l>) at an angle to each other run, so that the gas flows emerging from them collide violently. 22. Internal combustion engine according to claim 16, characterized in that the crankcase (i) has at least two housing parts (la, 1c) and the first overflow channel is designed as a groove (22a, 22b, 2U) on the inner wall of these parts . 23. Internal combustion engine according to claim 22, characterized in that the groove (22a, 22b, 2k) is formed between the crankcase parts (Ia ₁ 1b or 1b _p 1c). 24. Internal combustion engine according to claim 22, characterized in that the groove (22a, 22b, 24) extends on the peripheral region of the
inner wall of the crankcase part (ia, lc) extends. 25. Internal combustion engine according to claim 22, characterized in that that the groove has a first, outer section (22a, 22b) and a further inside, parallel section (24). 26. Internal combustion engine according to claim 16, characterized in that that there are two first and second overflow channels with a corresponding symmetrical design. 27. Internal combustion engine according to claim 20, characterized in that that the opening of the first transfer channel against the Wall of the second overflow channel (20,21) is directed. 28. Internal combustion engine according to claim 15 »characterized in that that the first overflow channel has at least one opening (32) at the bottom of the crank chamber (8). 29 internal combustion engine according to claim 28, characterized in that that in the bottom of the inner wall of the crank chamber (8) a groove (29) is formed, into which the opening (32) opens. 30. Internal combustion engine according to claim 29 »characterized in that that the bottom of the groove (29) is inclined towards the opening (32). 31. Internal combustion engine according to claim I5, characterized in that that in the exhaust duct (i8) a throttle device (36; 37) is arranged. 809828/0669 3 ^ · Drennkraftmaschine according to claim 31 »characterized in that that the throttle device is an exhaust gas control valve (3 is, lielches is partially closed when the machine runs under partial load, 33 · Internal combustion engine according to claim 31 »characterized in that the throttle device has an insert (37)
tighter, narrowed opening. & 09828/0683